Meaning of fields in 4.3BSD PCB structure

[Mark Andrews]

In the Process Control block for VAX 4.[23]BSD, there is a software extension:

/*
 * Software pcb (extension)
 */
        int     pcb_szpt;       /* number of pages of user page table */
        int     pcb_cmap2;
        int     *pcb_sswap;
        int     pcb_sigc[5];


What are all these fields for? I realize that CMAP2 (pte in system page table)
is saved in the `pcb_cmap2' field of 1 pcb and restored from the pcb of another
process during a context switch, but why?

The BSD book mentions that the `pcb_cmap2' field is used when dealing with
segments, but does not go into any further detail.

Thanks,

Mark
------------------------------------------------------------------------------
	Mark Andrews
	Systems Programmer,
	Alias Research,
	Toronto, Canada
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				Mark
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------------------------------------------------------------------------------
	Mark Andrews
	Systems Programmer,
	Alias Research,